Relying on infrared surface brightness fluctuactions to trace AGB properties in a sample of elliptical galaxies in the Virgo and Fornax clusters, we assess the puzzling origin of the UV-upturn phenomenon, recently traced down to the presence of a hot horizontal branch stellar component. We find that the UV-upturn actually signals a profound change in the c-m diagram of stellar populations in elliptical galaxies, involving both the hot stellar component and red-giant evolution.
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